Taphole construction for metallurgical vessels



25, 1969 R. A. BUCHHOLZ 3,463,475

TAPHOLE CONSTRUCTION FOR METALLURGICAL VESSELS Filed April 21. 1967 w vavme RVSSELL 4. EUCIIHOLZ ITTOP/VE)" United States Patent 3,463,475 TAPI-IOLE CONSTRUCTION FOR METALLURGICAL VESSELS Russell A. Buchholz, Pittsburgh, Pa., assignor to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Filed Apr. 21, 1967, Ser. No. 632,688 Int. Cl. C21b 7/12; C21c /50; F27b 7/00 US. Cl. 266-42 5 Claims ABSTRACT OF THE DISCLOSURE The present disclosure relates to improved taphole construction and taphole refractories for metallurgical vessels, for example, oxygen converter vessels. Particularly, the invention relates to a taphole fabricated from a plurality of prefabricated cylindrical conduit segments. Each segment has a substantially uniformly dimensioned molten metal passage of rectangular cross-sectional configuration, the longest surfaces of the passage being substantially in alignment with the vertical axis of the vessel.

In the processing of molten steel, in furnaces such as the basic open hearth and the basic oxygen furnace, refractories having a high degree of erosion resistance must be employed in the metal contact areas. One such area of these vessels, which is vulnerable to erosion is the tap hole of the vessel. The taphole of a metallurgical furnace may be disposed in various locations depending on the furnace type. For example, in the basic open hearth, a taphole is located below the molten metal bath, while in the basic oxygen furnace, it is located above the metal bath and the furnace is tilted to allow gravity flow of the molten metal through the taphole.

In the formation of furnace tapholes, by prior practice, a steel pipe, generally ranging from 2 to 6 feet in length was placed in the taphole area and an unconsolidated refractory mix was rammed or cast around the pipe to hold it in place. After the first tapping of a furnace heat, the steel pipe would melt out and a completely refractory taphole would result. However, these tapholes are physically unsatisfactory for various reasons. The ramming and casting mixes had to be, of course, placed in the furnace in an unburned state and thus could not attain the maximum density and strength necessary to develop sufiicient erosion resistance necessary to satisfactorily survive a furnace heat. Further, the density and the strength of the tapholes were non-uniform from end to end.

It has been suggested to prefabricate a combination of castable and metal pipe. There has also been some suggestion to employ prefabricated refractory sleeves to form the tapholes. These sleeves had a circular molten metal passage which was found to be satisfactory for a period of time. However, with the rapidity that steel is now being produced especially in basic oxygen furnaces, i.e., 25 heats in 24 hours, a taphole is needed that can survive a greater number of heats. The previously mentioned prefabricated tapholes, because of their circular molten metal passages were found to erode quite rapidly along the side wall portion of the passageway with respect to the vertical axis of the furnace. However, it has been discovered and it is upon this that the invention is largely predicated that taphole life can be increased by providing a molten metal passageway of rectangular cross-sectional configuration wherein the longest surfaces of the rectangular configuration are in alignment with the vertical axis of the vessel.

Accordingly, it is an object of the present invention to provide a means for fabricating a taphole for metallurgical vessels consisting of preformed, prefired refractory shapes.

Another object of the invention is to provide tapholes for basic steelmaking furnaces that may be readily replaced between furnace heats.

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A further object of the invention is to provide a taphole conduit for a basic oxygen furnace composed entirely of prefired, prefabricated refractory shapes.

Other objects of the invention, will in part, be apparent hereinafter.

In order to more fully understand the nature and scope of the invention, reference should be had to the following detailed description and drawings in which:

FIG. 1 is a perspective view, partly broken away, of a basic oxygen furnace, particularly showing the taphole side of the furnace; and

FIG. 2 is a perspective view of a prefabricated taphole conduit for use in metallurgical vessels according to the present invention.

:In accordance with the present invention and in attainment of the foregoing objects, there is provided a metallurgical vessel of the type having an outer metal support structure, a refractory lining interior of the support structure, a taphole opening passing through the lining and support structure and a taphole assembly passing through the taphole opening. The assembly is composed of a plurality of prefabricated, ceramically bonded cylindrical conduit segments. Each segment includes a passage for molten metal between the end surfaces thereof. Further, the opposed ends of the segments are preferably provided with complementary interlocking means, such as tongues and grooves, for mating with an adjacent segment. The molten metal passage is of substantially uniform dimensions and is rectangular in cross-sectional configuration. The longest surfaces of the configuration are in alignment with the vertical axis of the vessel. The conduit segments are arranged in series and are complementarily mated. to provide an integral taphole assembly having a continuous molten metal passage.

The taphole conduit segments may be fabricated by methods well known in the art. One method includes forming a stiff, mud-like mixture of selected refractory material, vibration casting and then burning at a suitable temperature to impart maximum strength. However, the most economical and preferred method of fabrication is by mixing the selected refractory material with a tempering agent and ramming the mixture in a mold conforming to the contours of the conduit segments to obtain good densities upon subsequent burning. In either method, the burning and ceramic bonding may be carried out after the segments are assembled into an integral unit, if the buming kiln can accommodate the complete unit. An advantage of firing the segments before assembly is that the segments may be shipped to the job site where they are assembled without great risk of damage.

The conduit segments may be composed of any basic refractory materials characterized by relatively good erosion resistance in contact with molten steel produced in basic steelmaking furnaces. The preferred refractory materials used in the furnaces mentioned are dead burned magnesite and dolomite and mixtures thereof. Other basic refractory materials having relatively good erosion resist ance would also be satisfactory. These refractories may be tar impregnated and contain various other refractory ingredients known in the art to impart superior physical properties. A particularly useful refractory sleeve is composed of extremely refractory dead burned magnesite material of high purity periclase having a magnesia content of at least about by weight.

Referring to FIG. 1, there is shown a basic oxygen furnace 10, consisting of an outer metal shell 12, a shell protective lining 14 in contact with the inside surface of the shell, and a brick working lining 16. The vessel is constructed of three major zones, the bottom zone 18, the barrel zone 20 and the cone section zone 22. The bottom zone is dish shaped and of upwardly opening concave configuration. The brick 23 in the bottom zone terminate at the barrel zone with their face surfaces inclined from the bottom upwardly to the cone section zone. The working lining brick 14 in both the barrel and the cone section zones are disposed so that their face surfaces are in horizontal plane. The cone section zone, having a taphole area 26 extends upwardly and terminates in the form of a mouth 28 at the top of the vessel. The cone section zone is of downwardly opening truncated cross-sectional configuration.

Disposed in the taphole area of the vessel is a taphole assembly 30 according to the present invention, which is composed of a plurality of identical conduit segments. An individual conduit segment is shown in FIG. 2.

Each conduit segment 32 contains opposite ends which are provided with a tongue 34 and a groove 36 for interlocking and mating with an adjacent segment in molten metal sealed relation. The conduit segments have generally opposed faces 38 and opposed sides 40. The opposed sides 40 contain a slight projection 42 for reasons that will be discussed subsequently. The molten metal passage is of rectangular cross'sectional configuration having opposed long surfaces 44 and opposed short surfaces 46.

In practice, the taphole assembly of the prosent invention can be placed in a basic oxygen vessel shown in FIG. 1, readily and with a minimum of labor. Generally, a refractory cement is not necessary at tongue and groove joints, since at the operating temperatures of the vessel the conduit segments will expand slightly to provide a sufficient seal. However, refractory cement may be employed, if desired, as an added safety factor or to facilitate installation.

After the brick are stacked up to the cone section zone and the taphole opening, the first conduit segment is laid on the refractory lining at the interior of the vessel. The uppermost brick at the taphole opening are provided with slight depressions to accommodate the projections 42 on the conduit segments and hold them in place while the remainder of the segments are being added. Similarly, the lowermost brick extending down from the cone section zone contain depressions for the same purposes. The remainder of the segments are then added by mating together the complementary tongues and grooves of a series of segments and securing them into a unit to pro vide a continuous molten metal passage.

Each segment is laid so that the longest surface 44 of the metal passage is in substantial alignment with the vertical axis of the vessel. As was mentioned previously, it was found that when a heat is tapped, the greatest amount of erosion in a taphole passage occurs at the side walls. It was found that by forming a metal passage in a rectangular cross-sectional configuration and arranging 4 the segments so that the long surfaces thereof become the side walls of the metal passage, greater life is obtained with such a taphole than was obtained with previous taphole configurations.

While the invention has been described in the drawings with reference to basic oxygen steelmaking vessels, it should not be limited thereto.

Having thus described the invention in detail and with suificient particularity to enable those skilled in the art to practice the invention, what is desired to have covered by Letters Patent is set forth in the following claims:

I claim:

1. 1n metallurgical vessels of the type having an outer metal support structure, a refractory lining interiorly adjacent the support structure and a taphole opening, a taphole assembly passing through said taphole opening composed of a plurality of prefabricated, ceramically bonded conduit segments having opposite ends, each segment having a substantially uniformly dimensioned molten metal passage of rectangular cross-sectional configuration, the longest surfaces of said passage being in alignment with the vertical axis of the vessel, said conduit segments being complementarily mated to provide a continuous molten metal passage.

2. The vessel of claim 1 in which the opposite ends of the conduit segments are provided with interlocking means for mating with an adjacent segment.

3. The vessel of claim 2 in which the complementary interlocking means of the conduit segments consists of tongues and grooves.

4. The vessel of claim 1 in which the outer periphery of the conduit segments is of rectangular cross-sectional configuration.

5. The vessel of claim 1 in which the outer periphery of the conduit segments contain at least one projection extending therefrom for mating with adjacent refractory lining to hold it in place during installation in the taphole.

References Cited UNITED STATES PATENTS 1,565,084 12/1925 Frerichs 26642 2,378,239 6/1945 Myron 6l11 X 3,343,827 9/1967 Hansen 26642 X FOREIGN PATENTS 1,111,224 7/1961 Germany.

I. SPENCER OVERI-IOLSER, Primary Examiner U.S. Cl. X.R. 26636 

